Many industrial processes result in the creation of liquid waste. Liquid waste may be in forms such as an unwanted process byproducts, used or contaminated solvents, and/or used or contaminated lubricants. Waste water is an example of liquid waste which is produced in various industrial processes. In many food canning processes, for example, a salt water byproduct is produced. Waste water is also a byproduct in paper production processes, and in bleaching and dying processes used by the textile industry in the manufacture of garments. Other applications in which waste water is produced include sewage processing and food processing.
Typically, liquid waste is treated before subsequent disposal, recycling, or reuse thereof. One method of treatment entails diluting the liquid waste until a level of contaminants contained therein meets a predetermined standard. Thereafter, the diluted liquid waste is typically disposed into a nearby stream or lake. This solution is not environmentally sound since the contaminants introduced into the environment may be accumulative.
U.S. Pat. Nos. 5,292,438, 5,256,288, and 5,259,952, issued to Lee and assigned to Cer-Wat, Inc., disclose methods and systems for separating a solid material and a liquid material contained in a slurry. A filtration system disclosed therein utilizes a continuous filtration medium, such as a traveling belt filter, on which a cake of the solid material forms within a separation chamber. This system may be utilized for treating liquid waste by filtering out the contaminants contained therein. Both the contaminants and the filtered liquid may then be reused or recycled.
Further disclosed in U.S. Pat. No. 5,259,952 is an open-loop control system for controlling parameters of the filtration system. The open-loop control system commands the parameters to provide desirable steady-state separation conditions for a given slurry. However, the use of open-loop control results in a system which does not necessarily provide desirable transient separation conditions. Further, the open-loop control system is not capable of adapting the commands to changing conditions, such as a change in the concentration of solid material contained within the slurry.